1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology, and more particularly, to an integrated circuit including a latch circuit suitable for latching an input signal.
2. Description of the Related Art
An integrated circuit may include diverse structures of circuits for latching an input signal.
FIG. 1 is a circuit diagram illustrating a structure of a circuit for latching an input signal in a conventional integrated circuit.
Referring to FIG. 1, the circuit for latching an input signal IN in the integrated circuit includes two inverters INV1 and INV2.
An input terminal of the first inverter INV1 and an output terminal of the second inverter INV2 are coupled with each other, and an output terminal of the first inverter INV1 and an input terminal of the second inverter INV2 are coupled with each other. Therefore, logic levels of an input node IN and an output node OUT are in a complementary relationship to each other.
For example, when the input node IN is in an electric potential of a high logic level, the output node OUT is stable in an electric potential of a low logic level. On the contrary, when the input node IN is in an electric potential of a low logic level, the output node OUT is stable in an electric potential of a high logic level. A latch circuit formed of the inverters INV1 and INV2 has two different and stable logic states depending on the high or low logic state of the input node IN and the output node OUT. The logic states are held as they are.
The latch circuit formed of the inverters INV1 and IN2 is very stable, and noise has not been a matter of concern.
However, as the latch circuit is exposed to radiation with ionization characteristics, it is influenced by generated electric charges. That is, radioactive rays are emitted into the latch circuit so that the memory state of the latch circuit becomes unstable, and the possibility of malfunctions, such as an inversion of the memory state increases.
This phenomenon is referred to as a soft error, which is caused by an alpha(α)-ray emitted from package materials or wiring materials.
Particularly, soft errors occur more easily as power supply voltage is lowered. For this reason, in a semiconductor memory device which is driven by a low voltage power supply, an important theme is how to increase tolerance to soft errors.